Method and apparatus for heating glass preparatory to delivery



March 12, 1963 P A Filed May 27. 1959 M. GELL ET AL 3,080,737

METHOD AND APPARATUS FOR HEATING GLASS PREPARATORY TO DELIVERY 7Sheets$heet 1 "wan/T02 3 M Ma. 53

March 12, 1963 P. A. M. GELL ET AL 3,080,737 METHOD AND APPARATUS FORHEATING GLASS PREPARATORY TO DELIVERY Filed May 27, 1959 7 Sheets-Sheet2 isms/goes W e60. 43W, 4M5) 6 March 12, 1963 P. A. M. GELL ETAL3,080,737

METHOD AND APPARATUS FOR HEATING GLASS PREPARATORY TO DELIVERY Filed May27, 1959 7 Sheets-Sheet 3 /N VENTOBS March 12, 1963 P. A. M. GELL ETAL3,080,737

METHOD AND APPARATUS FOR HEATING GLASS PREPARATORY TO DELIVERY Filed May27. 1959 7 Sheets-Sheet 4 [It 85a S ag INVENTOES war 97 March 12, 1963Filed May 2'7. 195s METHOD P. A. M. GELL ET AL AND APPARATUS FOR HEATINGGLASS PREPARATORY TO DELIVERY '7 Sheets-Sheet 5 March 12, 1963 P. A. M.GELL ET AL 3,080,737

METHOD AND APPARATUS FOR HEATING GLASS PREPARATORY TO DELIVERY Filed May27, 1959 7 Sheets-Sheet 6 March 12, 1963 Filed May 27. 1959 P A. M. GELLET AL METHOD AND.

APPARATUS FOR HEATING GLASS PREPARATORY TO DELIVERY 7 Sheets-Sheet 7lNVENTOQS United States Patent Ofiiice 3,380,737.- Patenterl Mar. 12,1963 3 689 7 37 METHOD AND APPAR ATUS FOR HEATING GLASS PREPARATORY TDELIVERY Philip Anthony Maunsell Getl, Caynton, near Shifnal, and

Douglas Graeme Hann, Bechhury, near Shifnal, England, assignors toElernelt Limited, Bilston, England, a British company Filed May 27,1959, Ser. No. 815,249 Claims priority, application Great Britain May30, 1953 10 Claims. (Ci. 65*128) performance of the methods by whichthey are produced that so far as possible the glass gob from which thearticle in question is'shaped or made, shall initially, that is to say,at the instant of delivery from the glass feeding furnace be homogeneousas to the temperature of its different parts. In many cases it isinevitable that immediately upon delivery cooling will occur by thedissipation of heat from the outer surface of the gob, so that sometemperature gradient will necessarily exist between the outer surfaceand the central region of the gob, but it is desired especially to avoidin the gob of glass the existence of certain zones occupying either aconstant position or a varying position in relation to a reference axis(which for the purpose of convenience may be considered as passingthrough the centre of the outlet perpendicular to the plane thereof)which have a higher temperature or alower temperature than the remainderof the gob.

If the gob or body of glass fed out from the glass feeding furnace doesincorporate zones in which the glass is of a higher or lower temperaturethan the remainder of glass in the body, the proper formation of thearticle may be prejudiced by the contrast in viscosity, or possibly evenif the article is successfully produced its mechanical strength andresistance to fracture may be impaired through internal stress, or otherproperties such as its optical properties may beimpaired.

Furthermore, the existence of zones in which the glass has a higher orlower temperature than the remainder of glass in the body fed out fromthe feeding furnace may cause the body to be displaced to one side orthe other of the reference axis'in the course of delivery. This may leadto the malformation or articles in cases where the glass is deliveredgravitationally to the apparatus by which the article is shaped, as forexample, a pressing machine, or blowing machine or machine utilising acombination of blowing and pressing operations wherein the glass isdelivered gravitationally to a mould.

One object of the present invention is to control the temperaturegradient existing in a body of glass delivered from a glass feedingfurnace which temperature gradient may be regarded as existing in across-sectional plane generally perpendicular to the delivery axis orpath along which the body moves in the course of delivery from thefurnace.

'Yet another object of the invention is to enable proper control to beexercised over the temperature of molten glass contained within a glassfeeding furnace in the vicinity of an outlet or a plurality of outletsand in particular at angularly spaced positions around a reference axisor axes extending through said outlet or outlets so as to minimise therisk of the setting up of asymmetrical 2 temperature gradients in bodiesof glass delivered from said outlet or outlets.

Yet another object of the invention applies particularly to the feedingof glass from a furnace chamber by means of a plunger reciprocated alonga reference axis extending through an outlet of the furnace, and isdirected to establishing in the working path of said plunger, andimmediately adjacent thereto, control over the temperature of the moltenglass and thereby to minimise any tendency for the expelled gob of glassto exhibit pronounced differences of temperature at positions spacedapart angularly about said reference axis.

Yet another general object of the invention is to provide an improvedarrangement of electrode means in relation to the outlet of a glassfeeding furnace and to .provide electrical supply circuits for saidelectrodes to enable the foregoing objects to be attained.

Yet another object of the invention is to provide an improved method offeeding gobs of glass from a glass feeding furnace, such gobs having acontrolled symmetrical temperature gradient in a cross-sectional planegenerally perpendicular to a reference axis passing through an outlet inthe bottom wall of a feeding chamber of said furnace.

The invention will now be described by wayof example with reference tothe accompanying drawings wherein:

FIGURE 1 is a view in side elevation and in vertical cross section ofone form of glass melting and refining furnace incorporating a feedingchamber and electrodes in accordance with the invention.

FIGURE 2 is a fragmentary plan view on an enlarged scale and with thetop wall of the feeding chamber removed to show the electrodes operativetherein.

FIGURE 3 is a fragmentary view on an enlarged scale of the feedingchamber in side elevation and in vertical cross section on the line 3-3of FIGURE 2.

FIGURE 4 is a fragmentary view in side elevation and in vertical crosssection of one of the electrodes and its supporting means.

FIGURE 5 is a diagram showing a polar diagram of FIGURE 7 is afragmentary circuit diagram illustrating a modification of the circuitshown in FIGURE 6 providing for automatic variation in the magnitude ofthe current density as aforesaid, and

FIGURE 8 is a further fragmentary circuit diagram illustrating amodification of the circuit shown in FIG- URE 6 when this is applied toa feeding chamber having two outlets.

Referring firstly to FIGURE 1 the furnace therein shown comprises fourmain portions, these being a furnace chamber 32 in which glass batchmaterials in solid or divided form are melted and partly refined, afurther chamber 33 connected to the furnace chamber 32 by way of a duct34, a forehearth 35 serving to connect the further chamber 33, and afeeding chamber 10.

The chambers 32 and 33, the duct 34 and the electrode means 36 and 37provided in these chambers for heating may be as described and claimedin our copending United States application, Serial No. 620,618, nowPatent No. 2,899,476 but it will be understood that it is by no meansessential that this particular arrangement of glass melting and refiningchambers should be adopted, the glass delivered to the feeding chamber10 being capable of being brought to a molten condition Referring now toFIGURE 5 this shows in plan a typical form of current densitydistribution around the reference axis 84. Heat loss from the body ofglass melt contained in the feeding chamber 1i! will normally begreatest adjacent to the end portion of the side wall on thelongitudinal axis 85 of symmetry of the in-flow path indicated by thearrows 86 but on the side of the reference axis I 34 remote therefrom.Heat loss will normally be at a minimum where the in-fiow path entersthe feeding chamber and there will be an intermediate value of heat lossadjacent each of the side wails 48 on the transverse axis 87.

To make good this heat loss and maintain the glass in the feedingchamber at uniform temperature at all positions spaced angularly aroundthe reference axis 84 a current density distribution would be requiredas shown typically by the full line 38 which he polar diagram, themagnitude of the current density at any position being represented bythe radius vector 83;.

It may happen, however, that due to some extraneous influence heat lossfrom one side wall t'd along the axis 37 is somewhat greater at one sidethan the other so that a symmetrical disposition of the electrode plate53b, as shown in full lines, will not achieve the desired full linepolar diagram 88 for current density distribution.

Moreover, the ratio of heat loss from the end wall of the feedingchamber remote from the in-flow path and forehearth may be somewhatgreater in comparison with the rate of heat loss at the region at whichthe in-fiow joins the feeding chamber, and these combined influences mayresult in the production of a distribution of current densityrepresented by the polar diagram shown in broken lines at as and acorrespondingly inhomogeneous temperature distribution.

In the embodiment of the invention now described various means areprovided to enable a current density distribution in accordance with thepolar diagram 88 to be restored. One of these means is the mounting ofthe electrode 13b, namely the pedestalfidb and its associated clampwhich permits the stem portion 55b to be adjusted endwise so that theelectrode plate 53b can be brought into the position shown in brokenlines.

This produces a shortening of the gap between adjacent ends of electrodeplates 53a and 53b at the side at which the current density was formerlybelow its proper value, and a lengthening in the gap at the other sideat which the current density was above its proper value, and

end to reduce the electrical resistance of the current path 7between'the electrodes 13a and 13b considered collectively and thecompanion electrode 12 at the first side relativelyto that existing atthe second side, where formerly the current density was greatest,because the total area of electrode face presented at this lastmentioned side is now reduced compared with that presented with a supplyvoltage of selected value, and the electrodes 13a and 12 are treated asanother companion pair of electrodes and are fed with another selectedvoltage, the value of voltage in each case being determined by measuringan electrical quantity pertaining to the current path on the one handbetween the companion pair of electrodes 13b and 12, and on the otherhand between the companion pair of electrodes 13a and 12 and adjustingthe voltage applied between the electrodes of these companion pairsaccordingly.

The electrical supply for feeding the electrodes may comprise a singlephase alternating current supply applied 6 at terminals 15 and 16through a variable auto-tram former T6 to a main input transformer T1 ofwhich one terminal of the secondary winding is connected directly to theelectrode 12 through the conductor 17.

The other terminal of the secondary winding of transformer T1 feeds thetwo electrodes 13a and 13b respectively through conductors 18a and 18b,theformer including in series the secondary winding of an auxiliarytransformer T3a, and the latter including in series the secondaryWinding of an auxiliary transformer TSb.

The primary winding of the transformers T3a and T3b are fed fromterminals 20 and 21 connected to the same single phase supply. Betweenthe transformer T341 and the terminals 20 and 21 is operativelyconnected a variable auto-transformer T4a, and a second auto-transformerT4!) is operatively connected between these terminals and thetransformer T3b thus permitting the voltage applied to the primarywinding of each of the transformers T3a and T3b to be independentlyadjusted.

The auto-transformers T4a and Tdb are each adjustable to provide avariable output voltage by means of a me-,

chanical adjusting member, which could be manually operated but ispreferably operated, in each case, by

an associated reversible electric motor, these being indicated at Mlaand Mlb respectively. The motors Mla and Mlb are arranged to beenergised automatically to cause them to adjust transformers T411 and Tlb respectively in the appropriate directions to correct any depar-vture from the desired level of dissipation of electrical energy in thesegmental current path extending between the companion electrodes 13aand 12, and dissipated in the segmental current path between thecompanion electrodes 13b and 12.

For this purpose a monitoring relay A1 is provided having a currentwinding Ale and a voltage winding Alv. The winding Alc is connected tothe secondary winding of a current transformer Ctl through theintermediary of a bridge circuit rectifier w1w4. The voltage diiferencebetween the electrodes 13a. and 13b on the one hand and the electrode 12on the other hand is determined by connecting a coupling'transformer T5with its primary winding between the conductor 17 and a tapping point onresistor R1, the ends of this resistor being connected to the conductors18a and 18b.

This voltage may be measured by a voltmeter V1. The

.tapping point on the resistor R1 may be adjustable but pre-set ifdesired so that the system hereinafter described can provide eitherequal power dissipation in the two segments of the current path, or anypredetermined ratio of power dissipations found in practice to produceoptimum results, so far as temperature uniformity in thedelivered gob isconcerned.

The secondary winding of transformer T5 feeds a bridge circuit rectifierw5-w8 and thence the voltage winding Q Alv of the monitoring relay A1.

The monitoring relay A1 includes amplifying means (not shown) controlledby the current and voltage wind- .ing A10 and Alv to produce movement ofan armature trical resistance afforded bythe glass inbetween theelectrode 12 on the one hand and the electrodes 13a and 13b on the otherhand. When the resistance of the glass is below a predetermined value orbelow the lower limit ofa predetermined range of values the movablecontact is caused to engage the fixed contact AIL (which ultimatelyresult in the voltage between the electrode 12 and the electrodes 13aand 13b being lowered) while if the rcsistance of the glass is above apredetermined value or above the upper limit of a predetermined range ofvalues the contact Ala engages the contact AIR (which will ultimatelyresult in the voltage between the electrode 12 and the electrodes 13aand 13b being raised) whereby departure from the desired operatingconditions is corrected automatically. When the glass resistance has thedesired value, the movable contact Ala assumes the neuterminals 23 andtral-position shown-imFIG: 6"in whicll'it isispace'd' from both fixedcontacts A 1R,andA1L. Terminals 30 and 31 formonitoring relayAl' areconnected to an alternating current supply which serves to, energiseitheamplifier means incorporated in this relay and also the motors forelt'ecting automatic adju'stment'of'the transformers T -ia and T4b'ash'ereinafter described." 1 v 1 One type of 'monitoring relay. whichwould be suitable' isknown as aforce balance relay or computer. Themotors MlaandiMlb are of the reversible type swam-raw a: tio'ns -iwillbejapparentifrom a gram;

-Ifit isdesired-to dispensewith -the automatic adjust ment of voltageprovided by transformer-s T iaand Tb, 1' whereby these are bothraised'or both lowered, use may be made of a further spring centred keyswitch '82- hav- 7 ing fixed contacts 'SZR and SZL and a movable contacthaving'three' terminals, one'of which is connected, "in a each case,through acornrnon conductor 22 to .one of the I 24,"supplied from singlephase ALC.

mains.-- I V V a 1 The other terminalJZl: of these mainstisconnected toeach motor alternatively, one or other of its two remaining terminalsproviding for rotation in respectively opposite directions and in such away that the motors can be energised eitherjto rotate both in thesamedirection that is toraise the voltage' suppliedby the transformersT4a well'as relays A3 and'A4.

The energising winding of relayAZR is'connected be tween terminals23 and24 through the intermediary of contacts AIR and Ala whilst theenergising windingv of irelayAZL is similarly connectedthrough theintermediaryo-f contactsAlL and Ala so that according to.thesettingof'th'e monitoring relay A1, neither,.or. either,

of the relays AZR and AZL are energised;

, Also, inseries with the-energising-windings of these 'lastmentionedrelays is anadjustahle time delay'relay S operated manually.

can becut outof the circuit by a changeover switch S4 having movableoontactsSR and 84L operating between fixed contacts S4Rl, StRZ, S4111and 84542.1;

Yet another spring centred key switch Sd-rnay be provided to control theoperation and direction of operation ofxmotor Mzgwhich is associatedwith'the variable autotransformer-"Toto adjust, same. The fixed contacts85a, and S511 are connected to two terminals of the motor M27 7 V toprovide rotation rin opposite i directions respectively 20v and Ttbjorlowerxsuch voltages or, alternatively,.to rowtate in oppositedirections so as to provide corresponding adjustments of 'the twovoltages supplied by the transformers T4a and T lb inzoppositedirections. i For this purpose relaysAZR andAZLare provided as.

when encrgiseddwhilst'the movable contact S50 is connected with one ofthe supply terminals 23, 29the other being connected toreMZ; I e ITheuser of the furnace may'decide whether to setthe 'inovablefcontactSic ofithe switchSI closed with re- "spect to the Ifixed contacts Sta.or SItb according to whether, in expelling ai gobithrough theopening'lL tlie gobj-tendsto be deflected in the di-rectionvof thelongi-- tudinal centre line of'the chamberuliti towards the electrode13a; or toward the electrode 13b; It will tend to be'defiectedtowardstheelectrode in the vicinity of which the. glass isof greater viscosity andlower'temperature and, therefore, the remedy is to increase the voltagedit- AS," the purposeof which' is :to prevent-short. term or,

random variations in the input applied to the monitormg relay A1producingundesired energisation of either:-

The three terminals of the rnotor Mlr rare'designated relatively to, theother along the axisiii (FIGURE; 5) j'. may be eifected'by obsetwing thegob expelled'fromithe' outlet-11., Thefgobwill tend to incline towardsthe and 25R and 25L, whilstithe'lterminals of the motor; Ml baresimilarly designated 26 and 26R? and 261;; the p 1 significance of the'sufiiXes-K andL being thattheseiters minals are energised when it-is'desire'd that; the 'moto-rs.

concerned should 1 respectively raise and lower the .volti ages of theirassociated transformers T40 and T45.

11 on the other side where ture and less viscous; i i

Consequently the electrode 'llfib needs ;to be moved; i towards :thesideo'ffithe feeding'jchamber, tov'l-ards which TerminalQZSRlisconnectedwith terminal24 lalterna} e ery through -v contacts; AZRa or throughcontacts Alia,

the terminal: ZSL isCsimila'rIy connected alternatively with:

"terminal? 4'tli'roughcoritacts AZLr'z and A'iai served during''expulsion of the gob.

5 voltage values in circuits containing=these additional elec-' trodesand the electrode 12. 1 ,e

'- However, in operation visualobservation of the 'syma spring centredkey switch sl having fiiiedcontacts slt'aand Slb and movable.contactrslc .riorrnallySheld open 'withjrespect to both the fixed. contactsbut-t displaceable inanually -toclosewi-th respect to; eitherof them.Movablel contact {S10- is ,conneotedq directly by conductor- 27toterminal'24, of the'incomingaAC; supply. 1

It' 'will' be evident .fromsthe' foregoing description that Y thesys'tem provides for'autorriatic adjustmentsf the transform ers" Tea-and T411 3 so that voltages supplied by these may either. bo'th' ber'a-ised or both be" lowered,

- whereas i-f it- .is desired to' raise tlie voltage provided bytransformer -T4a or lower" this, whilst respectively lowering andraising'the voltage produced by transformers T41 this ,is done byma'nually operating the movable contact S10- closed with respect to one.or the other: of

the]contac-tsislai,and Slb. The manner in. which the i t s 1 1-se-M 1rssns e s en aw tobe corrected automatically. In thismodification themanually ference'betweenrzthiselectrode and the electrode 12; by theappropriate 'settingo ftheswitch S1 to "adjust-traile formers I41; andT415 ,in'opposite directions;

- Detection ofdeparture fromythe proper relative values of'cu'rrentdensity at one side of the, i eeding chamher side where the glasscoldest and the current density- 7 lowest since more-"glass willbe'forced 'out of the outlet the glass'is of higher temperate,

the gob in-cline's'if there is any lateral asymmetry ob- If? it :isdesired to measure thef'conditioncompanionielectrode 12' by measurementof cur-rent and metry or otherwise of the gob is found satisfactory.

It fwtllof course also:be' evident that the voltage per unit lcngth of:the glassapplied between -eleetrode 13c and its companion electrode 12and electrode" 131: andits cornpanion" electrode 12 maybe varied byvertical ad ustment of the electrode utilising the associated pedest'a'ls 56a and 56b for thisipurpose. V 7 v v Thus; instead of providingtransformers T411, T311 and lTtb, flfib, the-motors M1 2 and Mtb couldbe/utilise'd' i to dr ve the lower threaded posts 57a and 57b through iV the intermediary of any suitable transmission means. Referring now toFIGURE 7 there" is shown therein a modification enabling correction fordeparture'from desired currentdens-ity relationships along the axis ioperable switch st of FIGURES is replaced by, amonitoring-relay A6 whichstudy of the circuit dia- This key switch S2 can be 5 broughtintothecircuit'andthe automatic control'system 5. 10

toithe remainingterminalot the mo V sof the glass 'l at opposite sidesof thefreferenee 137G554? and along the;

reference axis SIX-this woul-dj-be done; by providing" electrodesfadditional-to those illustratedionthe' axis '37? and measuringthe resistanceof glass between these and the may be similar to the relayA1, but provided with two sets of windings A6Va, A6Ca, A6Cb, and A6Vb.

The windings incorporating the letter C pertain to current and thoseincorporating the letter V to voltage quantities derived respectivelyfrom the electrodes 13a and 13b of their associated supply circuits, thearrangement being such that the magnetically actuated movable contactA6A is moved on to the fixed contact Ada or A6b according to whether theinfluences of windings bearing the suifix b or windings bearing thesuifix a of the monitoring relay A6 predominates.

These windings are supplied in the case of the current windings fromcurrent transformers T7a and T7 b through rectifier bridge circuitsw9-w12 in one case and W13- w16 in the other case.

The voltage windings of the monitoring relay A6 are supplied fromvoltages appearing across resistors RM and R2b of which a'pre-setvariable proportion can be tapped off by the sliders to rectifier bridgecircuits wit"!- w2ti in one case and w21w24 in the other case.

The remaining parts of the circuit'may be as illustrated in FIGURE 6.

Referring now to FIGURE 8 this illustrates an electrode arrangementapplicable to a feeding chamber 10 provided with two orifices 11 11 Inthis arrangement electrodes 13a and 1311 would be provided as before anda circuit arrangement could be adopted identical with that shown inFIGURE 6, with or without the modification of FIGURE 7. In effect thiswould provide control of the distribution of current density in segmentsdisposed at angularly spaced positions about the central area or regioncontaining the two out- 111, Q However, if it is desired that individualcontrol as to current density distribution should be effected inrelation to each of these outlets, a central electrode 13c may beprovided, this being connected by way of the conductor 130 totransformer T1.

, The supply circuit may be otherwise as shown in FIG- URE 6 with theexception that if desired individual manual or automatic control may beprovided for the motors Mla and Mlb to permit the voltage betweenelectrode 13a and its companion electrode 12 to be raised or loweredwithout changing that between electrode 13b and itscornpanion electrode12 and vice versa. 7 The need for correction may also be judged visuallby'observing whether gobs delivered from the outlet are hotter at oneside than the other, in which case appropriate correction may be madeeither by operation of the switch S1 or of the operating memberfordisplacing the electrode 1% from side-to-side according to whether theinequality of temperature exists along the longitudinal axis of symmetryo-fthe furnace chamber or from sideto-side of the furnace chamber.

Similarly, these criteria may be applied by the user to effect therequisite correction in the case where two orifices 11 and 11 areprovided as previously described,.

rounding outlets 11 and 11 respectively and both connected to conductor17) so as to raise the temperature in the immediate vicinity of suchelectrode 13a or 13b to reduce the viscosity and hence restore the gobto appropriate size. It will be understood thatin this arrangementsubstantially identical plungers could be provided in association witheach orifice 11 so that inequality in the viscosity of the glassdelivered by the two plungers respectively, and hence also in thetemperature between the glass which forms the gobs respectively may beavoided.

What we claim then is: v

1. In a glass feeding furnace including aside wall and a bottom walldefining a feeding chamber, said bottom wall having an outlet fordelivery of a body of glass from said chamber, the furnace furtherincluding means acting in axial alignment with the said outlet forimpelling the discharge of gobs of glass from said outlet; the provisionof means for controlling the temperature of said body at positionsaround a reference axis extending upwardly through said outletcomprising, lower electrode means disposed in the vicinity of saidoutlet and having a current communicating face surrounding saidreference axis, upper electrode means in said chamber and disposed in azone surrounding said reference axis, said upper electrode meansincluding a plurality of upper electrodes having respective downwardlypresented current communicating faces collectively occupying at leasthalf the circumferential length of said zone, means for feeding currentto said upper and lower electrode means to pass such current through theglass in a path extending generally lengthwise of and surrounding saidreference axis, supporting means for said upper electrodes, and meansincorporated in said supporting means for adjusting the position of atleast one of said upper electrodes relative to another one of saidelectrodes in a direction extending parallel to said axis to vary thedensity of said current in the glass in one segment of the current pathrelatively to another segment thereof.

2. in a glass feeding furnace including a side Wall and a bottom walldefining a feeding chamber said bottom wall having an Outlet fordelivery of a body of glass from said chamber, the furnace furtherincluding means acting in axial alignment with the said outlet forimpelling the discharge of gobs of glass from said outlet; the provisionof means for controlling the temperature of said body at positionsaround a reference axis extending upwardly through said outletcomprising, a lower electrode disposed in the vicinity of said outletand in contact with glass contained in said chamber, upper electrodemeans in said chamber and disposed in an annular zone surrounding saidreference axis, said upper electrode means including a plurality ofupper electrodes spaced apart angularly about said reference axis andhaving current communicating faces presented generally towards saidlower electrode and collectively occupying at least half thecircumferential length of said zone, means for feeding current in aplurality of separate circuits each including said lower electrode andrespectively including said upper electrodes, to pass current throughthe glass in a plurality of adjacent segmental paths between said lowerelectrode and said upper electrodes and collectively surrounding saidreference axis, and means for varying the voltage in one of saidcircuits between said lower electrode and one of said upper electrodesrelatively to the voltage in at least one other of said circuits betweensaid lower electrode and a corresponding other one of said upperelectrodes. 3. In a glass feeding furnace including a side wall and .abottom wall defining a feeding chamber said bottom wall having an outletfor delivery of a body of glass from said chamber; the provision ofmeans for controlling the temperature of said body at positions around areference axis extending upwardly through said outlet comprising, lowerelectrode means disposed in the vicinity of said outlet and in contactwith glass contained in said chamber, upper electrode means in saidchamber and disposed in a zone surrounding said reference axis, saidupper electrode means including a plurality of upper electrodesspacedapart angular-1y about said reference axis and having currentcommunicating faces presented generally towards said lower electrodemeans and collectively of an area to occupy a substantial proportion ofthe area of said zone, a source of alternating voltage for feedingalternating current in a plurality of circuits each including said lowerelectrode means and respectively including said upper electrodes, topass current through the glass in a plurality of respective segmentalpaths between said lower electrode means and said upper electrodes andcollectively surrounding said reference axis, monitoring spears? V agein circuit with said electrodemeans for feeding altermeans responsive toelectrical resistance presented by at least one of said, paths in theglass, control means opera tively connected with said monitoring meansfor varying the electricalv-oltage applied per unit length'of the pathbetween said lower electrode means and one of said I 7 upper electrodesrelatively to that applied between said lower electrode means andanother'one of said umber electrodes. f q 4. A glass feeding furnaceincluding a sidewall and a bottom: wall defining a feeding chamber, saidbottom wall having an outlet for deliveryofa body of glass from-saidchamber, means acting in axialtalignment withthesaid outlet'forimpelling the discharge of gobs of glass; frornsaid outlet,,lowerelectrode rneans disposedfin' the;

vicinity of said outlet and in contactwith glass contained,

in said chamber, upper electrode means in said'chamben and disposed inan annular zone surrounding a reference,

aXis extending upwardly through said outlet, said upper electrode meansincluding a'plu-rality of upper electrodes" 7 incorporated in saidsupporting meansfto enableat least hating currentt-o said upper andlower electrode meansto pass such current through the glass in a pathextend 7 ing' generally lengthwise of-and surrounding said plunger, 4

supporting means for said upper electrodes, and means one of saidupper'electrodes to be positionally adjusted inadi'rection to vary itsspacing in relation to said refereneej'axisto vary the density of saidcurrent in the glass in one ,segrnent ofthecurrent path relatively toanother segment thereof.

7. A glass, feeding furnace including aside Walland a bottom'wall"defining' a feeding chamber having an entry thereto for; glass, saidbottom wall'having' an outietfan elongated plunger in saidchamberextending,lonitudinallyi I alonga reference; axis extendingupwardly through said outlet;- means{'for'reciprocating said plungertoward and away from said outle't to deliver gobs of "glass'fr'ornjsaid'having current communicating faces presented generallyv 7 towards saidlowerelectrode means andc'ollectively occupying at least half'thecircumference of said zone, means l for feeding current to said upperand lower electrode; means to pass such current through the glass inatpath extending generally lengthwise of and surrounding; said referenceaxis, supporting means, for said upper electrodes and means incorporatedin said supporting means for'ad- 7 justing the position of one of saidupper electrodes relative toanother one of said-electrodes in adirection transa verse of said axis. L Y V V 5. A'g1a'ss feeding furnaceincluding a side-wall'and a bottom Wall defini11g 'a feeding chamberhaving an entry thereto for glass, said bottom wall having an outlet,

an elongated plunger in said chamber extending-longi tudinally along areference axis. extending upwardly through said, outlet, means forlongitudinally reciprocating said plunger toward and away from saidoutlet todeliver, gobs of glass from saidoutlet, lower electrode meansdisposed in the vicinity'of'sjaid outlet and in contact with glasscontainedin said chamber, upper electrode means in said chamber anddisposed in a zone surrounding said reference axis, said upper electrodemeans includinga plurality of upperelectrodes spaced apart angular'lyabout said reference axis and having current communicating "outlet,lower electrode means disposed in the vicinity 'of said outletfan'dhavingla cur-rent communicating face surroundingsaid referenceaxis,'upper'electrodemeans in 'said "chamber and disposed" in a 'zonesurrounding said,

reference axis, said upper electrode means including a plurality ofupper electrodes spaced apart angular ly about said reference axis andhaving-current communicating faces, presented, generally towards "saidlower'electrode' 7 means and collectively of anarea togoccu'py asubstantial V proportionof the area'of said'zone, a source ofalternating Tvoltage'for feeding alternating current in a'plurality ofcircuits each includingv said lower electrode means and respectivelyincluding said upper electrodes, '1 to pass cur-. went through; theglass ina plurality 'of'respective seg mental paths between said lowerelectrode means, and: said upper electrodes and' collectivelysurrounding said:

plunger, and means-forvaryingthe voltage applied "in said circuitsbetween, said lower electrode means 'a'nd'one of said upper electrodesrelatively to" another one of. said upper electrodes." 3

8. In va glass feeding furnace, a sidewall and albottom' wall definingalcl'iarnber, said bottom 'wall having an ,out-l I let 'for delivery of*a}b ody offglass'fr'orn s aid chamberin the direction of afreferenceaxis extending through said "outlet; the latter having an outer boundaryinset laterally fr'or'n, said side wall; means actingin'axialalignmentwith the 'said'outlet'for impellingthe;dischargqlof gob soi jglass fromsaid outlet a lower electrode adjacent said faces;presented ;generallytowards said lower electrode means and collectively of an area to occupya substantial 1 -,proportion of thearea of said'zone, a source ofalternating voltagelinfcircuit wlthsaidelectrode meansfor feeding"alternating current to said upper and lower ele'etrode .ineanjs to passsuch current through the glass in a path extending generally lengthwise.of and surroundinglsaid plunger, land-means for varying the electricalvoltage per unit length of said pathapplied between said lower'elec-t'trode -rneans and at least one of said upper electrodes relatriccurrent; a plurality of controlcircuits, each circuit 7 tively to thatapplied between said lower electrode means and at least one other ofsaid upper electrodes.

6. 'Ajgla'ss feedingfurnace includinga side wall and a bottom walldefinin'g'a feeding chamber having an entry ftheretofor glass, saidbottom wall having an outlet,'an

elongated plunger in said chamber extending longitudiv l and away fromsaid outlet todelivergob's of glass from said outlet,.1ower electrodemeans disposed in the vicinity of said outlet and having acurrentcommunicating face 7 surrounding said reference axis, upper electrodemeans in said chamber and disposed in a zone surrounding said plunger,said upper electrode means including a plurality nally along a'reference axis extending upwardly through said outlet, means forreciprocating saidplunger toward 1 outlet and having a currentcommunicating face in said cham-berfsaidf faceextending-in an annularzone about said axis; a plurality of separate upper ele'ctro des in saidchamber axially spaced from said lower electrode and having respectivecurrent communicating faces singularly spacedj about said axis in anannular ZQIlG ial'ld extending 1 laterally outwardly beyond saidlouter:boundaryof said i outlet and ointly. extending'gover at leastone'lialf of the circumference of said annular zone;a'source'ofelecbeing connected ts said source and'to a respective one ofsaid'faces for, passage of current through 'said c-hamber paths relativetothe'den-sity of the current passing .in an} defining a chamber,said'bottom wall having afpluv :ralit-y offoutlets.fordeliveryofrespective bodies of glass from said; chamber in the direc'tion,ofrespective referof upper electrodes spac'ed'apart angularly aboutsaid reference axis .andfhaving current communicating faces presentedgenerally towards said lower'electrode means and collectivelyof an areato occupy a substantial propor-' tion of the area of said. zone, asource of alternating voltencefa'xes extendingthr'ough' said outletsmeans acting in axial alignment with at least. one yof saidoutletsrmim'pelling t-he discharge of gobsfof glass from said one outlet, atlower electrode adjacent each of said outlets, each of said electrodeshaving a current communicating face in said chamber, said face extendingin'an annular zone a about the respeotive axis; a pluralityvlof'upperelectrodes 7 1 in said chamber axially spaced from corresponding ones ofsaid lower electrodes, said upper electrode means each including aplurality of current communicating faces angularly spaced about therespective axis in an annular zone and jointly extending oversubstantially one half of the circumference of the last mentioned zone;a source of electric current in circuit with said faces for passage ofcurrent through said chamber between said lower electrodes and theplurality of faces of the corresponding upper electrode means in aplurality of separate axially extending respective paths, and means forvarying the density of a current passing in one of said paths relativeto the density of the current passing in another one of said paths.

1 0. A method of forming a body of glass having a controlled temperaturedistribution, comprising the steps of forming a tubular body of moltenglass having an axis and an axially extending cavity; axially passing aplurality of electrical currents through said body in respectivecircuniterentially oifset paths so as to heat segmental portion of saidbody about said cavity by respective ones of said 14 currents;monitoring the temperature of one of said segmental portions; adjustingthe magnitude of said current in said one portion relative to themagnitude of the current in another one of said portions responsive tothe sensed temperature; and radially collapsing said cavity to form asolid body of glass from said segmental portions.

References Qited in the file of this patent UNITED STATES PATENTS1,375,336 Wadsworth Apr. 19, 1921 1,680,543 Howard Aug. 14, 1928 I1,999,744 Wadman Apr. 30, 1935 2,276,295 Ferguson Mar. 17, 19422,790,019 Stalego Apr. 23, 1957 2,830,107 Hahn et al Apr. 8, 19582,913,509 Pinotti Nov. 17, 1959 FOREIGN PATENTS 671,405 reat Britain May7, 1952

10. A METHOD OF FORMING A BODY OF GLASS HAVING A CONTROLLED TEMPERATUREDISTRIBUTION, COMPRISING THE STEPS OF FORMING A TUBULAR BODY OF MOLTENGLASS HAVING AN AXIS AND AN AXIALLY EXTENDING CAVITY; AXIALLY PASSING APLURALITY OF ELECTRICAL CURRENTS THROUGH SAID BODY IN RESPECTIVECIRCUMFERENTIALLY OFFSET PATHS SO AS TO HEAT SEGMENTAL PORTION OF SAIDBODY ABOUT SAID CAVITY BY RESPECTIVE ONES OF SAID CURRENTS; MONITORINGTHE TEMPERATURE OF ONE OF SAID SEGMENTAL PORTIONS; ADJUSTING THEMAGNITUDE OF SAID CURRENT